[ruby-core:119140] Re: CPU-bound load affects the timeout thread

Could you report that to https://github.com/ruby/timeout/issues ?

On Thu, Sep 12, 2024 at 1:16=E2=80=AFPM yuri.kanivetsky--- via ruby-core <
[e-mail]> wrote:

> Hi,
>
> I'm not sure if it's a bug. Take a look at the following gist:
>
> https://gist.github.com/x-yuri/253f76df6287441f64b5eaee418813c0
>
> It's supposedly a minimal reproducible example of what I ran into a coupl=
e
> of days ago. In my case it was basically a sort of a background jobs
> service. It received messages, processed them and sent the result to
> another service. Every message was processed and sent in a separate threa=
d.
> And it made a number of http requests as part of processing messages
> (net/http which uses timeout()).
>
> It worked normally for a couple of hours (10-20 threads), but at some
> point the number of threads reached the thread pool's max_threads (320),
> http requests started to time out (later then they should, after 60-100
> seconds instead of 3 seconds), and probably things started to get slow.
>
> Then I noticed the following line:
>
> patterns.any? { |pattern| quote.match(pattern['regex']) } ? 1 : 0
>
> It was performed for every quote (10 times) in every thread, there were
> 300+ patterns and they (pattern['regex']) were strings. I moved convertin=
g
> strings to regexps to initialization (before starting to accept messages
> and creating threads) and it seems to work now with ~10 active threads.
>
> I'm trying to understand what exactly happened and how to avoid it or wha=
t
> awaits me in the future. Is there some critical load that breaks things? =
I
> guess in theory the number of threads should increase linearly with the
> load. But it looks like in this case there's some critical load that just
> makes things stop working. Or maybe for some time some negative effects g=
et
> accumulated and then things break. My conjecture is that it has something
> to do with GIL. But what exactly happens? Or what can I do to further
> investigate the issue? I'm going to try to run ruby with RUBY_DEBUG_LOG a=
nd
> try to examine the debug output. I guess I need to figure out why the
> timeout thread doesn't always get enough time. Does something block the
> threads? How are they scheduled? When do they switch? Any pointers or lin=
ks
> to the code are welcome.
>
> Regards,
> Yuri
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